Integrated remote sensing and google earth engine analysis of groundwater changes under climate and human influences: a case study of Iran

Abstract Groundwater (GW) is recognized as the second-largest freshwater reservoir in the world, following surface water. Over the years, it has been subjected to immense pressure to meet human demands. Additionally, one of the most significant consequences of human activities is climate change, which can alter the physical and chemical properties of GW, thereby impacting its ecological functions. This study examined GW patterns in Iran from 2000 to 2022, emphasizing the roles of both climatic and anthropogenic factors in altering GW levels. The present study evaluated various climatic and anthropogenic variables, including air temperature (AT), precipitation, snow cover, urban development, agricultural land, and surface water storage to explore their relationships with changes in GW. The Mann-Kendall (MK) trend test was employed to analyze these relationships. The MK trend analysis revealed a significant declining trend in GW (S = − 167, Z = − 4.04), accompanied by decreasing trends in surface water (Sen’s slope = − 15.29) and cropland area (Sen’s slope = − 337.25). Snow cover, precipitation, AT, and built-up areas exhibited non-significant trends over the study period. The analysis also revealed a correlation coefficient of -0.43 between AT and GW. Precipitation and snow cover were found to have a relatively moderate effect on GW levels, with a correlation coefficient of 0.43 and 0.54, respectively. A significant negative correlation of -1.00 was observed between built-up areas and GW from 2000 to 2022, indicating that an increase in settlement development has led to decrease in GW. The findings also indicated a positive correlation coefficient of 0.75 and 0.872 between cropland, surface water and GW, respectively, demonstrating that a decrease in cropland is linked to a decrease in GW and surface water. Overall, the results underscore the substantial influence of anthropogenic factors, such as urban expansion, agriculture, and surface water on GW in Iran. Anthropogenic factors, as well as climatic factors contributed to a reduction in GW by 33 mm, with a marked decline starting in 2009. Before this pivotal year, the average GW was around 629 mm, which dropped to 596 mm afterward.